Photodetectors include a photodetector element constituted by single elements such as a photodiode, a linear sensor constituted by photodetector elements that are aligned on a line, such as a photodiode array, and an image sensor constituted by photodetector elements that are arranged two-dimensionally, such as a CCD (charge-coupled device) sensor and a CMOS sensor.
With respect to a sensor for use in a measuring device, which measures light from a measuring object, a photodiode has been mainly used from the viewpoint of superior precision, cost performance and technical easiness. However, in an attempt to obtain reflection factors or the like of a plurality of items by using the photodiode, an optical system or a test piece needs to be shifted.
Moreover, since the photodiode is used for obtaining data that is averaged within a spot diameter, it is not suitable for use in precisely detecting color developments, as typically exemplified by detection of spot color developments.
With respect to an immuno-chromatograph test piece measuring device, only the device of a driving photometric type that measures light with an optical system being shifted on a test piece has been proposed.
In order to solve these problems, the application of an image sensor is proposed. Since data of the image sensor is image information relating to a target area, measurements of a plurality of items, detection of spot color developments, correction of positional deviations in test pieces, etc. may be carried out based upon information of one frame.
Detections of the shape and color of a subject by the use of an image sensor have been well-known. For example, a method in which an image of a test strip for use in immunization measurements is picked up by a CCD camera so that determination is made based upon the area or the ratio of the longitudinal and lateral lengths has been proposed (see Japanese Patent Application Laid-Open No. 9-257708). In this method, after the picked-up signal has been binarized as a luminance signal, the shape of an image is measured; therefore, this method is not used for measuring the density within the image.
With respect to another example in which two-dimensional measurements are carried out by using an image sensor, an urine measuring device is listed. In this device, in general, measurements are carried out by determining not the density (brightness) in color developments, but the color gradation (hue) in urine test paper, and a color-CCD device is used.
In an attempt to detect a two-dimensional density distribution of a test piece with high precision by using an image sensor, in addition to irradiation irregularities in light, lens aberration, etc., in-plane light irregularities occur due to a sensitivity difference between pixels of the image sensor. For this reason, in order to carry out detections with high precision, in general, the sensor or the measuring object is shifted by using a mechanical driving system. In such a case, even if the image sensor is applied, it is merely utilized as a one-dimensional linear sensor.
It has not been clarified whether or not the reflection factor or the like can be measured two-dimensionally by using an image sensor such as a CCD sensor and a CMOS sensor.
Therefore, the first objective of the present invention is to provide a measuring method, which makes it possible to measure light from a measuring object two-dimensionally or along a straight line by using an image sensor, and a device for use in such a method.
Moreover, the second objective of the present invention is to achieve a measuring method for a measuring object, which uses an image sensor as a detection device, and carries out quantitative measurements on the measuring object such as an immuno-chromatograph test piece based upon measurements of light from the measuring object, and a device for use in such a method.